Hippocampal Cellular Responses To Datura Metel Alkaloid (datumetine) And N-methyl-d-aspartate Receptor Interaction In C57bl6 Mice

Datura metel is a plant that is used as a form of herbal treatment in Nigeria. However, its recreational abuse is increasing among Nigerian youths due to its availability. Which is worrisome because of some untoward side effects like memory loss and hallucinations in humans. This study was designed to investigatethe effects of datumetine (alkaloid) in Datura plant on hippocampal N-methyl-D-aspartate receptors (NMDAR) functions. The objectives of the study were to determinethe effects of datumetine on: (i) memory; (ii) some NMDAR signalling molecules (iii) hippocampal cellular morphology; (iv) hippocampal synapse; and (v) hippocampal electrical activity.rnThirty adult male C57/BL6 mice were assigned into three groups of 10 mice each. The mice were administered dimethyl sulfoxide (DMSO/Control), 0.25mg/Kg body weight of datumetine and 1mg/Kg body weight of datumetine intraperitoneally for 14 days. Novel object recognition (NOR) and Y-maze tests were conducted on the animals on days 10 and 13 of administration to assess the level of memory. At the end of treatment, mice were euthanized in isofluorane chamber, perfused transcardially with 1X phosphate buffered solution followed by 4% paraformaldehyde (for immunofluorescence samples). Western blotting was used to assess hippocampal levels of glutamate ionotropic receptor subunit-1 (GluN1), calcium-camodulin kinase-alpha 2-subunit (CamKIIα), phosphorylated calcium-camodulin kinase-alpha-2 subunit at threonine-286 (pCamKIIα-T286), cyclic adenosine-mono-phosphate response element-binding protein (CREB) and brain-derived neurotrophic factor(BDNF) while the distribution of major neuronal subtypes, astrocytes, and microglia were expressed using immunofluorescence antibodies. Expansion and electron microscopy techniques were used to assess neural connections and synapse morphology respectively, while in vivo electrophysiology wasperformed for hippocampal electrical activity. Quantitative data were compared using analysis of variance(ANOVA) and/or unpaired t- test at significant level of p<0.05.rnThe findings of the study were that:rni. datumetine binds with NMDAR at its binding sitesrnii. memory index from NOR (44.31±5.86%, 45.71±7.91%) and Y-maze (53.05±1.91%, 30.53±4.47%) were significantly reduced in datumetine exposedanimals than control(86.69±8.44%, 66.86±3.53%) (F(2,12)=7.514, F(2,8)=15.96 p = 0.0077, 0.0160)rniii. datumetine significantly increased hippocampal expression of GluN1 (0.0666±0.0088, 0.0987±0.0227) and CamKIIα (0.4276±0.0016, 0.2679±0.0076) than control (0.0406±0.0068, 0.1609±0.0051) (p = 0.0578, 0001) while pCamKIIαT286 (0.4062±0.0051, 0.3552±0.0171), CREB (0.2447±0.0258) and BDNF (1.1680±0.0195, 0.8741±0.0287) were significantly reduced in datumetine treated animals than control (0.4326±0.0144, 0.4615±0.0050, 1.2680±0.0337) (p = 0.00760, 0022, 0.0001),rniv. increased hippocampal expression of astrocytes, microglia, glutamatergic, GABAergic, cholinergic, and dopaminergic neurons are in datumetine exposed mice.However, there was arnxxrnreductionin expression of serotonergic neurons of datumetine exposed mice (791.6±98.2, 953.7±22.3) compared to control (1368.0±64.5) (F(2,27)=22.49, p=0.0016),rnv. datumetine exposure depleted neurofilament expression, arrangement and altered synaptic morphology; andrnvi. prolonged duration of interspike interval (2.607±0.772 s), interburst interval (16.08±2.86 s) and burst duration (0.0599±0.0093 s) were observed in datumetine treated mice than control (0.533±0.077 s, 9.265±0.86 s, 0.0464±0.0028 s) (p = 0.0007, 0.0059, 0.0880).rnThe study concluded that datumetine increased hippocampal NMDAR activity, resulting in excitotoxicity, impairment of selected neural diffuse systems thereby leading to memory loss. The study recommended that the use of Datura metel plant be discouraged among the populace

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